Medical balloons may be combined with a wide variety of devices and used in a vast array of medical procedures. For example, medical balloons may be combined with a catheter to provide dilation catheters, drainage catheters, and the like.
Dilation catheters rely upon a medical balloon for applying pressure against the interior of a biological conduit, such as a blood vessel, a portion of the urinary tract, and/or a portion of the gastro-intestinal tract. Dilation catheters are useful in a variety of techniques, including gynecological procedures, cardiac procedures, general interventional radiology procedures, and the like.
One example of a cardiac procedure is percutaneous transluminal coronary angioplasty (PTCA). Using this technique, a physician can dilate a narrowed artery by inserting and advancing a catheter with a deflated medical balloon at its tip into the narrowed part of the artery. The plaque is compressed upon inflation of the medical balloon, which dilates the inner diameter of the blood vessel, allowing blood to flow more easily. Following this procedure, the medical balloon is deflated and the catheter removed from the patient's body.
Another procedure employing dilation catheters is stent delivery. A stent may be a wire mesh or a solid tube used to support an artery that has recently been cleared using angioplasty. After being collapsed to a small diameter, the stent may be placed over the medical balloon of the dilation catheter and advanced to the area of the blockage. When the medical balloon is inflated, the stent expands, locks in place, and forms a scaffold, holding the artery open.
One specific use of dilation catheters is in the treatment of obstructed blood vessels. This type of procedure normally begins with insertion of a delivery sheath using the Seldinger or other technique. Delivery sheaths are generally small-diameter plastic tubes and are another type of conduit, through which a catheter may be inserted. Generally, the delivery sheath is inserted through a patient's skin and then into a major blood vessel, for example. The delivery sheath is arranged such that the proximal portion remains on the exterior of the patient, while the distal portion is located in the major blood vessel of interest. Next, the distal portion of a wire guide may be inserted into the exterior and proximal end of the delivery sheath. Then, the wire guide may be passed through the delivery sheath, out the distal end of the delivery sheath, and into the patient. In this fashion, a delivery sheath may be used as a means for the placement of intravascular medical devices into venous or arterial systems following insertion of the delivery sheath through the skin. The delivery sheath may also protect the point of entry into the patient's body from mechanical damage and trauma.
Once inside the patient, the distal end of the wire guide may be advanced into the diseased coronary artery until it reaches the obstruction. After crossing the lesion, or other region to be dilated, the wire guide may be secured such that it remains in this location. During this entire procedure, the proximal end of the wire guide remains at the exterior of the patient.
Next, the distal tip of a dilation catheter may be slid over the proximal end of the previously placed wire guide. The dilation catheter, following the previously placed wire guide, may be advanced into the proximal end of the delivery sheath, through the body of the delivery sheath, out the distal end of the sheath, and then into the patient. The dilation catheter may be advanced over the wire guide until the medical balloon, located toward the distal end of the dilation catheter, is properly positioned adjacent to the lesion. Finally, fluid may be used to inflate the medical balloon to a predetermined size, thus compressing the lesion.
Generally, the medical balloon of a dilation catheter occupies a folded configuration prior to inflation. This configuration may reduce the force necessary to advance the dilation catheter through the conduit, which in turn may reduce the physical trauma to the patient. When the medical balloon on the dilation catheter is inflated, to compress a lesion for example, the medical balloon unfolds. Once unfolded, the medical balloon is generally not capable of again obtaining the folded configuration.
FIG. 1 depicts a longitudinal cross-sectional view of a conventional dilation catheter 100 that includes an elongate catheter body 105, having a proximal end 107 and a distal end 108. The distal end may terminate in a distal tip 110. The conventional dilation catheter body 105 is equipped with a conventional medical balloon 115 (depicted in its unfolded configuration), having a distal balloon end 117 and a proximal balloon end 118. The medical balloon 115 has a distal conical region 120, a proximal conical region 125, and a working length 130, where the working length 130 is defined by the distal conical region 120 and the proximal conical region 125. The medical balloon 115, including the working length 130, the distal conical region 120, and the proximal conical region 125, is formed by a balloon wall 135, enclosing a balloon cavity 140. The balloon wall 135 may form a distal balloon lip 142 and a proximal balloon lip 143. The conventional medical balloon 115 may be attached to the elongate catheter body 105 via the distal balloon lip 142 and the proximal balloon lip 143. For clarity of discussion, the lips 142, 143 are not considered part of the balloon because they do not enclose the balloon cavity 140.
The distal conical region 120 and the proximal conical region 125 each include two taper transitions. There is a distal working length-to-taper transition 145, a distal taper-to-neck transition 150, a proximal working length-to-taper transition 155, and a proximal taper-to-neck transition 160. The distal working length-to-taper transition 145 is located between the working length 130 and the distal conical region 120. The proximal working length-to-taper transition 155 is located between the working length 130 and the proximal conical region 125. The distal taper-to-neck transition 150 is located between the distal conical region 120 and the elongate catheter body 105. The proximal taper-to-neck transition 160 is located between the proximal conical region 125 and the elongate catheter body 105.
The conventional medical balloon 115, in its unfolded configuration, includes sharp bends at the balloon working length-to-taper transitions, 145 and 155, and at the taper-to-neck transitions, 150 and 160. The sharp bends at the transitions of the conventional medical balloon 115 do not easily collapse after the balloon has been inflated and can make it difficult to pull the balloon back through the conduit after use. The harder it is to remove the collapsed balloon after use, the more patient trauma may occur at the entry site during removal of the device. Furthermore, if the conventional medical balloon 115 freezes in the delivery sheath and the physician exerts excess force on the conventional dilation catheter 100 in attempt to remove it from the sheath, mechanical failure of the device may occur. A situation that may necessitate making a much larger incision in the patient to remove the device. A medical balloon that facilitates removal of dilation catheters from conduits may beneficially reduce patient trauma.